4 Hydroxy 3 methylbut 2 enyl diphosphate reductase

4-Hydroxy-3-methylbut-2-enyl diphosphate reductase (EC 1.17.1.2, isopentenyl-diphosphate:NADP+ oxidoreductase, LytB, (E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate reductase, HMBPP reductase, IspH, LytB/IspH) is an enzyme in the non-mevalonate pathway. It acts upon (E)-4-Hydroxy-3-methyl-but-2-enyl pyrophosphate (or "HMB-PP").

(1) isopentenyl diphosphate + NAD(P)⁺ + H₂O ⇌ (E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate + NAD(P)H + H⁺(2) dimethylallyl diphosphate + NAD(P)⁺ + H₂O ⇌ (E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate + NAD(P)H + H⁺

4-Hydroxy-3-methylbut-2-enyl diphosphate reductase is an iron-sulfur protein that contains either a [3Fe-4S] or a [4Fe-4S] cluster.